"Ryanair's decision to launch fully allocated seating is also part of the airline's commitment to listen to its customers."

Ryanair says that passengers who book and pay for seating can choose to sit in the first number of rows to depart the aircraft first. Or they might choose over-wing seats in order to have extra legroom. Priority Qs will continue to allow people to board first.

A spokeswoman said the airline would not lose money by moving to allocated seating.

The carrier said that while bookings were ahead of last year, the cheaper fares would continue – with prices during the summer down 9pc, and falling by up to 10pc between October and the end of the year.

"There's going to be a period of cheaper pricing," the airline's chief executive Mr O'Leary said.

The carrier blamed the continuing fall in fares for the need to revise its profit outlook for the year – the second profit warning in as many months.

It said full-year outturn was now expected to be between €500m to €520m, instead of the previously thought €570m to €600m.

The airline's share price slumped as much as 12pc on news of the profit warning.

Average fares fell by 2pc in the half-year to the end of September, although revenues from areas such as the roll-out of reserved seating, priority boarding and higher credit and debit card fees grew by 22pc to €713m. Passenger numbers also rose by 2pc in the period.

Despite the profit warning, Mr O'Leary remained bullish – saying that passenger numbers and on-board spending were strong, but that there was weak demand for air travel across Europe.

"People are characterising this as 'What's gone wrong?'

"Nothing! We are booming ahead," he said in a conference call, citing October passenger numbers up 6pc from a year ago.

"There is a weaker pricing environment out there. Get over it. Wherever that pricing falls, it will be significantly below what our competitors can withstand."

Ryanair is slashing charges for checking in bags at the airport and re-issuing boarding cards in an effort to appease passengers and tackle criticism of its penalty fees.

FEES

So-called 'quiet flights' that will have fewer in-flight announcements and no annoying on-time arrival trumpet, as well as reduced fees and a 'grace' period for making free changes to bookings, are all to be introduced, as the airline tries to win over customers in a new push to improve its image.

Next year, the airline will roll out various initiatives including mobile boarding passes; a "Fare Finder" feature, which will enable customers to find dates and flights where the lowest fares are available; a new mobile app for smartphones and tablets; and new language websites in all Ryanair's major EU markets starting with Spain and Italy.